1. Field of the Invention
A method of overlay and sandwich formation of a combination of pervious concrete with itself and/or standard cement concrete.
2. Description of the Prior Art
In the construction and building industry the term "concrete" is used generically to define a collection or aggregation of materials which together form a reasonably continuous solid. Prior art products include both natural concrete and a variety of synthetic concretes, the most common of such products being asphaltic concrete, in which inert aggregates are mixed with a bituminous binding component, and Portland cement concrete. In Portland cement concrete the object is to obtain a continuous monolithic material of substantially uniform properties. In conventional and by far the majority of normal applications of concrete, voids and/or small discontinuities or inclusions of air are considered to be highly undesirable since these voids, etc. harmfully affect the operating or performance characteristics of the end concrete product.
However, in the specialized category of pervious concrete such voids are intentional in the formation of the concrete product. While such discontinuous concrete is generally well known in the prior art, this concrete suffers from inherent problems which make the overall product relatively undesirable. Such prior art porous concretes are generally considered of variable quality and indeterminate permability and thus unreliable or defective for controlled or specified construction applications.
The following U.S. patents disclose prior art products and/or methods of forming concrete products or cementitious material which are generally applicable but clearly distinguishable from the product and process of the present invention, described hereinafter: U.S. Pat. Nos. 271,089, to Lynch; 358,288 to Moore; 1,665,104 to Martienssen; 3,196,122 to Evans; 3,240,736, to Beckwith; 3,360,493 to Evans; 3,439,450 to Richards; 3,477,979 to Hillyer; 3,687,021 to Hensley; 3,690,227 to Weltry; 3,870,422, to Medico; 2,130,498 to Klemschofski; and 3,822,229 to McMaster.
As evidenced by the prior art set forth above there is an obvious desirability and need for discontinuous concrete products. Such products generally and/or theoretically would be much more efficient where drainage of water is desired pertinent to concrete product applications such as in highways, airports, parking facilities, bridge decks, etc.
However, products of the type disclosed in the above set forth U.S. patents frequently suffer from certain inherent disadvantages such as surface fracture when used under heavy load or stress conditions (commonly called ravelling) in roads, highways, and pavement where they are generally formed using substantially conventional concrete placing techniques or processes, with or without the application of additives to allegedly increase adhesion between the aggregate particles and improve other performance characteristics.
Moreover, pervious concrete in any of its described forms is of value in paving and other engineering applications because of its ability to permit water percolation isotropically through its substance. In engineering applications, however, certain structural uses of concrete such as bridges, culvert covers, walks and similar, cannot be usefully constructed with a pervious concrete, since any necessary reinforcement included in such concrete will experience relatively rapid attack and deterioration. Again, for pavement (either of pervious or monolithic concrete) repair or refurbishing by the addition of an integrated surface layer of pervious concrete is an obviously desirable objective.
Finally, engineering applications involving the construction of a pervious core between layers of monolithic concrete may be required.
Thus, there is a great need in the construction and building or repairing industry, specifically in building roads, highways and bridges for a porous concrete having an even distribution of liquid flow therethrough and which can better provide for traction or stress conditions from high speed operation of automobiles or large vehicles such as trucks, airplanes, or the like.